Scaling mechanism



Jan. 24, 1939. w. w. RODGERS SCALING MECHANISM Filed Oct. 28. 1937 2 Sheets-Sheet l Jan. 24, 1939.

W. W. RODGERS SCALING MECHANISM Filed Oct. 28, 1957 n 2 Sheets-Sheet 2 Fvg. 2a l 22 l? 5' 16 7g A. f (C59 Wl( I I .Z9 29 20 9 l LZ /7/4 lucente/n Patented Jan. 24, 1939 UN'TED STATES ATENT GFFIiCE Application October 28,

4 Claims.

The invention relates to a drafting instrument for use in reproduing drawings and the like at any of various scales, the device being of particular advantage in reducing or enlarging various kinds of maps having such irregular shapes as to make it very difficult to accurately reduce or enlarge with the usual drafting instruments.

The principal object of the invention is to provide an instrument of the class set forth which is of relatively simple and inexpensive construction, may be easily and accurately operated, and may be readily adjusted for enlarging or reducing at desired scales.

With the above and minor objects in view, the invention resides in the novel subject matter hereinafter described and claimed, description being accomplished by reference to the accompanylng drawings.

Fig. l is a top plan View partly broken away and in section.

Fig. 2 is a vertical transverse sectional view on line 2 2 of Fig. l.

Fig. 3 is a detail transverse sectional vview on line 3--3 of Fig. l.

Fig. 4 is a fragmentary side elevation showing the pencil or marker and part of its raising and lowering means.

Fig` 5 is a detail side elevation showing the tracer and part of its raising and lowering means.

Fig. 6 is a fragmentary side elevation showing the hand lever for operating the raising and lowering means of the marker and/or tracer.

One form of the invention has been shown and will be specifically described, with the understanding, however, that variations may be made within the scope of the invention as claimed.

A suitable base it is provided to rest upon the drafting board or table, said base being preferably lof circular outline and being sufficiently heavy to remain in place without danger of slipping. A turntable it is rotatably mounted upon the base it by means of a central pivot I2 or other desired bearing means. Two parallel horizontal bars i3 and i@ overlie this turntable II and are mounted thereon for longitudinal sliding. In the present showing, each of the bars i3, Id is of inverted T-shape in transverse section and in slidably mounting these bars, I make use or" peripherally grooved rollers I5 mounted on the turntable it, the longitudinal edges of the base portions of said bars, being snugly received in the grooves of said rollers. The upstanding webs I6 and II of the bars I3 and I4 respectively, are provided with rack teeth, those of the web IS being shown at I8 and those of 1937, Serial No. 171,585

the web I'I being illustrated at I9. A gear 29 is rotatably mounted in any preferred way upon the turntable II and meshes with the rack teeth It, and a similarly mounted gear 2l, preferably of the same size, meshes with the teeth i9. Two intermeshed gears 22 and 23 overlie the gears 2t and 2l respectively and are connected operatively with the latter. It will thus be seen that the two bars I'3 and I4 can relatively slide only in the manner determined by the ratio of the gearing operatively connecting them. In order that this ratio may be changed, the gears 22 and 23 are detachably mounted so that gears of other ratios may be substituted. To illustrate one of many ways in which the gears 22 and 23 may be detaohably connected with the gears 2U and 2i respectively, I show upstanding pins 2li on said gears 2B and 2l, receivable in openings 25 in the gears 22 and 23.

The gears shown will cause the bars I3 and ifi to move in opposite directions at the ratio determined by the gearing but should it be desired to produce a structure in which said bars would move in the same direction, this could be done by forming the rack teeth I8 of the bar I3 at the opposite side of the web I6 and by correspondingly changing the location of the gear 2i).

In order to hold the rack teeth i8 and I9 snugly engaged With the gears 26 and 2i respectively, overcoming any lost motion in the device, I have shown two rollers 2t and 2l', one contacting Ywith the vweb I6 opposite its point of contact with the gear 29 and the other contacting with the web I9 opposite the point at which this web contacts with the gear 2 I. These rollers may be mounted in any preferred way upon the turntable II.

referably all of the gearing and other parts carried by the turntable -Ii are housed within a suitable casing 28 having notches 29 through which the bars I3 and I4 pass. The lower edge of this casing may well surround the upper portion of the turntable II and may be provided with bifurcated lugs 3B held in place by thumb nuts or the like 3l carried by said turntable. The casing 28 may thus be readily removed when a change of gearing is to be effected, and said casing will normally serve to protect all internal parts against foreign matter and possible injury.

The bar I3 carries a pencil or other marker 32 at one of its ends, and the opposite end of the bar I4 carries a tracer 33. Both of these work-engaging members are provided with carriers 34 vertically slidable in fixed sleeves 35 suitably secured to the bars, each carrier 34 being provided with a lug 36 projecting through a vertical slot 31 in the sleeve. The horizontal arms of two bell cranks 38 underlie the lugs 36, one of said bell cranks being ulcrumed on the bar I3 and the other on the bar I4. The vertical arms of these bell cranks are pivoted to rods 39 extending longitudinally of the bars, and finger levers 40 are connected with said rods, one of these levers being mounted on the bar I3 and the other on the bar I4. It will thus be seen that by moving one lever 40, the pencil or the like 32 will be lifted and by moving the other lever 4i), the tracer 33 may be lifted.

On the ends of both bars I3 and I4, I preferably provide spring arms 4I, the outer ends of which are suitably shaped and positioned as at 42 to slide upon the work, said arms aiding materially in holding the entire device against any tendency to tilt in operation.

Any desired means may be provided for initially positioning the bars I3 and I4 in proper relation when gears 22, 23 of one ratio or another are to be applied. For illustrative purposes, I have shown the bar I3 provided with longitudinally spaced openings 45 having scale indications, it being intended that the proper one of these openings shall be alined with the datum point 46 on the turntable II to properly position said bar I3. Similar provision may be made to initially position the bar I4 properly, but the initial position of this bar is always the same.

By properly relating the instrument with a drawing or the like to be copied and the sheet upon which the copy is to be made, gears of the proper ratio having been previously installed, it is a simple matter to make the desired reproduction. With the arrangement shown, the arm i3 moves in the opposite direction from the arm I4, always a distance equivalent to the ratio of the change gears. Thus, for reproducing to a ratio of l-2, the tracer 33 will move twelve inches while the pencil or the like 32 will move six inches. As the bars I3 and I4 are rotated about the pivot I2, the angles of the tracer and pencil are the same, but their subtended arcs are at 1 2 ratio. Thus, a reproduced drawing is found to be completely inverted but drawn to perfect scale.

Excellent results may be obtained from the general construction shown and described and such construction may, therefore, be followed, but attention is again invited to the possibility of making variations within the scope of the invention as claimed.

I claim:

1. A scaling instrument comprising a horizontal base to rest on a desk, a turn-table mounted on said base for rotation about a vertical axis, two parallel horizontal bars mounted on said turn-table for longitudinal sliding movement, both of said bars extending in opposite directions from said turn-table and having rack teeth, a

tracer carried by one end of one of said bars, a marker carried by the other end of the other of said bars, both said tracer and said marker having pointed downwardly disposed ends, and gearing mounted on said turn-table and meshed with said rack teeth for insuring relative sliding movement of said bars in accordance with the ratio of said gearing.

2. A scaling instrument comprising a horizontal base to rest on a desk, a turn-table mounted on said base for rotation about a vertical axis, two parallel horizontal bars mounted on said turn-table for longitudinal sliding movement, both of said bars having horizontally facing rack teeth, a tracer carried by one of said bars, a marker carried by the other of said bars, two horizontal gears mounted on said base and meshing with the rack teeth of said bars respectively, two intermeshed horizontal gears lying upon the first mentioned horizontal gears respectively, and connecting means between said intermeshed gears and the underlying gears permitting lifting of the former from the latter.

A scaling instrument comprising a base, a turntable mounted on said base for rotation about a vertical axis, two parallel horizontal bars mounted on said turntable for longitudinal sliding movement, both of said bars having rack teeth, a tracer carried by one of said bars, a

marker carried by the other of said bars, two .5

gears mounted on said base and meshing with the rack teeth of said bars respectively, said gears each having upstanding pins, and two intermeshed gears overlying the rst mentioned gears respectively, said intermeshed gears having open- I ings receivingsaid upstanding pins to removably connect said intermeshed gears with the underlying gears.

4. A scaling instrument comprising a base, a turn-table mounted on said base for rotation about a vertical axis, two parallel horizontal bars overlying said turn-table and each of inverted T-shape in transverse section, the upstanding web portions of said bars being each provided at one vertical side with rack teeth, doublefianged guide rollers carried by said turn-table and engaging the base portions of said bars for mounting these bars for longitudinal sliding, a tracer carried by one of said bars, a marker carried by the other of said bars, gearing on said turn-table and meshed with said rack teeth for insuring relative sliding movement of said bars in accordance with the ratio of said gearing, and

pressure rollers moimted upon vertical axes ony said turn-table, said pressure rollers contacting with said upstanding web portions of said bars at points opposite the points at which the rack teeth of said web portions mesh with said gearing, thereby holding said gearing and rack teeth snugly intermeshed.

WILLIAD/I W. RODGERS. 

